Wireless devices are ubiquitous in many parts of the world. For example, portable wireless devices such as mobile phones, personal digital assistants (PDAs) and portable computers (e.g., laptop computers) are a convenience, if not a necessity.
In addition to being more prevalent, wireless devices are becoming smaller and lighter. Often, this translates into a reduction in the physical size and thus power of the battery powering the device. At the same time the battery is becoming smaller, the demand for ‘use-time’ (e.g., talk time of a mobile phone, or increased computing time for a laptop computer or PDA) is increasing. As can be appreciated, the demand for increased use-time can readily be met by increasing the power of the battery. Increased power of the battery often requires increasing the physical size of the battery. Accordingly, the goal of reducing the size of the battery competes with the goal of increasing the available power of the battery. This has lead to investigating options to increase the battery life in smaller batteries in wireless devices.
In a many portable wireless devices, the radio frequency (RF) power amplifier consumes a substantial portion of the power of the overall system of the device. As a result, poor efficiency in the RF power amplifier degrades the efficiency of the overall system, drains the battery more rapidly, and reduces the use-time. For this reason, much research in this field concentrates on increasing the efficiency of the RF power amplifier. If the RF power amplifier is more efficient, power drain on the battery is reduced. This in turn increases the use-time of the device per batter charge.